Piping Queen

I went into a split I had made with a few frames that had queen cells built on them and heard piping. For the very first time. I looked at the frames and found that two of the cells had been breached. One from the tip of the cell, and the other looked as though it had been ripped open from the side. On an un-emerged queen cell that had been stripped down to the pupal case by the nurse bees was a very pretty queen looking like she wanted to get to the queen that hadn't emerged yet. I don't know which was piping--or calling back.

My question: How do queens pipe? What part of their body do they use to make this sound?